The invention relates generally to pulse detonation engines and, more particularly, to enhancement of detonation for pulse detonation engines.
Pulse detonation engines detonate a fuel and oxidizer mixture, producing hot combustion gases, which have increased temperature and pressure and are propagated at supersonic speeds. The hot combustion gases are directed from the engine to produce thrust.
A representative configuration for detonation for a pulse detonation engine is illustrated in FIG. 1. As shown, a spark initiates the detonation process. If the spark has enough energy for the fuel and air mixture, a shock is initiated and travels to the right. As the shock processes the fuel and air mixture and turbulence is developed, formation of a transverse wave structure is initiated. Reflection of the transverse shock waves from the walls of the detonation chamber (shown here as cylindrical) creates interactions between the transverse shock waves, which result in “hot spots,” which have high local values of temperature and pressure and seed detonation.
Exemplary fuel and air mixtures for pulse detonation engines include liquid fuel and air mixtures. One problem with liquid fuel/air detonation is a long deflagration-to-detonation transition (DDT) length, which is typically larger than several meters.
Attempts have been made to decrease the DDT length by placing obstacles inside a detonation chamber, such as the augmentation device discussed in U.S. Pat. No. 5,901,550, by Bussing et al. and assigned to Adroit Systems, Inc. The augmentation device consisted of threading the interior surface of the inlet end of the detonation chamber with a helical-type thread to provide a ridged surface. Other attempts to decrease the DDT length include using pre-detonators and improving the combination of spark energy and position, detonation chamber geometry, and fuel/air properties.
Although some success has been achieved, shorter DDT lengths remain a central challenge for liquid fuel detonation systems. It would therefore be desirable to reduce the DDT length and, more particularly, to provide a detonation chamber having a reduced DDT length.